Within the past decade, several technologies have made it possible to monitor the expression level of a large number of transcripts at any one time (see, e.g., Schena et al., 1995, Quantitative monitoring of gene expression patterns with a complementary DNA micro-array, Science 270:467-470; Lockhart et al., 1996, Expression monitoring by hybridization to high-density oligonucleotide arrays, Nature Biotechnology 14:1675-1680; Blanchard et al., 1996, Sequence to array: Probing the genome's secrets, Nature Biotechnology 14, 1649; U.S. Pat. No. 5,569,588, issued Oct. 29, 1996 to Ashby et al. entitled "Methods for Drug Screening"). In organisms for which the complete genome is known, it is possible to analyze the transcripts of all genes within the cell. With other organisms, such as human, for which there is an increasing knowledge of the genome, it is possible to simultaneously monitor large numbers of the genes within the cell.
Such monitoring technologies have been applied to the identification of genes which are up regulated or down regulated in various diseased or physiological states, the analyses of members of signaling cellular states, and the identification of targets for various drugs. See, e.g., Friend and Hartwell, U.S. Provisional Patent Application Ser. No. 60/039,134, filed on Feb. 28, 1997; Stoughton, U.S. patent application Ser. No. 09/099,722, filed on Jun. 19, 1998; Stoughton and Friend, U.S. patent application Ser. No. 09/074,983, filed on filed on May 8, 1998; Friend and Hartwell, U.S. Provisional Application Ser. No. 60/056,109, filed on Aug. 20, 1997; Friend and Hartwell, U.S. application Ser. No. 09/031,216, filed on Feb. 26, 1998; Friend and Stoughton, U.S. Provisional Application Ser. No. 60/084,742 (filed on May 8, 1998), No. 60/090,004 (filed on Jun. 19, 1998) and No. 60/090,046 (filed on Jun. 19, 1998), all incorporated herein by reference for all purposes.
Levels of various constituents of a cell are known to change in response to drug treatments and other perturbations of the cell's biological state. Measurements of a plurality of such "cellular constituents" therefore contain a wealth of information about the effect of perturbations and their effect on the cell's biological state. Such measurements typically comprise measurements of gene expression levels of the type discussed above, but may also include levels of other cellular components such as, but by no means limited to, levels of protein abundances, or protein activity levels. The collection of such measurements is generally referred to as the "profile" of the cell's biological state.
The number of cellular constituents is typically on the order of a hundred thousand for mammalian cells. The profile of a particular cell is therefore typically of high complexity. Any one perturbing agent may cause a small or a large number of cellular constituents to change their abundances or activity levels. Not knowing what to expect in response to any given perturbation will therefore require measuring independently the responses of these about 10.sup.5 constituents if the action of the perturbation is to be completely or at least mostly characterized. The complexity of the biological response data coupled with measurement errors makes such an analysis of biological response data a challenging task.
Current techniques for quantifying profile changes suffer from high rates of measurement error such as false detection, failures to detect, or inaccurate quantitative determinations. Therefore, there is a great demand in the art for methods to enhance the detection of structure in biological expression patterns.
Discussion or citation of a reference herein shall not be construed as an admission that such reference is prior art to the present invention.